A suspected suicide bomber struck a pro-Palestinian rally in southwestern Pakistan, killing at least 50 people and wounding scores of others. This was the second major bombing this week, as the country tries to cope with the worst flooding in its history.

Several hundred Pakistanis, mostly minority Shi'ite Muslims, were attending the rally in the southwestern city of Quetta to support the Palestinian people.

Witnesses say a suicide bomber detonated explosives shortly after the rally arrived at a busy crossing in the center of the city.

Television pictures showed bodies and victims in blood-soaked clothes crying for help. Several journalists covering the rally were also wounded. One of them spoke to reporters in the city's main hospital.

This reporter said he heard intense gunfire just before the powerful bomb went off, and there were dust clouds and fire around him.

Witnesses say the deadly blast outraged other participants of the rally, who then attacked nearby shops and burned several vehicles. Police say unknown gunmen at the scene also began firing indiscriminately, causing a number of casualties.

The provincial home secretary, Akbar Hussain Durrani, tells VOA that strict security measures were put in place ahead of the rally.

"Because it was Friday, and every mosque and every worship place was guarded, almost 4000 - 5000 people were deployed in that area of the city," said Durrani.

He says police are investigating the incident, and they are also examining television footage to identify armed men who were firing at people in the surrounding area after the bomb blast.

The attack came just two days after triple suicide blasts left at least 35 people dead in the eastern city of Lahore. That attack targeted a religious procession of Shi'ite Muslims. Militants linked to Taliban and al-Qaida extremist networks claimed responsibility for the bombings.

The rise in militant attacks comes as Pakistan is trying to cope with the worst floods in its history. The natural disaster has made millions of people homeless and caused billions of dollars of losses to the country's economy.

In his weekly radio address to the nation Friday night, Prime Minister Yousuf Raza Gilani condemned the deadly attacks. He said that attacks on religious gatherings are further proof that those behind the violence do not believe in any religion.

The prime minister said the violent campaign is designed to destabilize the country, but the nation is determined to defeat terrorism.